Which iMacs should we get?

I am putting together a proposal for my university for 10 iMacs and we are looking at a couple options...

1) Current 2.8 GHz (High-end) with:
a) 2GB
b) 4GB (maxed out)

2) Current 3.06 GHz (Ultimate) with:
a) 2GB
b) 4GB (maxed out)

The following models are rumored for tomorrow or the coming weeks:

3) New 2.8 GHz (High-end) with:
a) 4GB
b) 8GB (maxed out)

4) New 3.06 GHz (Ultimate) with:
a) 4GB
b) 8GB (maxed out)

Once the iMac is updated, the current models will be discounted
extremely. On the other hand, the new models will carry better graphics cards, but as of right now it seems like nothing else. What are your thoughts about which model we should pursue? Please choose one current model option and one rumored "new" model, as well as which model you think is absolutely best.

Note: These computers will be used for 3 years at least and will not be upgraded (RAM) after purchase. It is also important to note that the computers' hard drives will be wiped of non-"frozen" files and programs that will always be on the computers when rebooted. Here are the programs that will be put on the computers:

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